Alkali Emission During Combustion of Coals at the Normal Temperature Range of PFBCs

摘要

Four coals of three different ranks were combusted at 850 and 900 exp 0 C to investigate the emission of sodium and potassium compounds during combustion. One high volatile bituminous coal, two subbituminous coals and one lignite were combusted in a laboratory-scale, batch (50 grams of coal), fixed-bed combustor. Alkali emissions were found to be greater at 900 exp 0 C than at 850 exp 0 C. For coals with less than 9 wt % ash content on a dry basis, the sodium compound emission increased linearly with decreasing ash content. Sodium from coal was found to be fixed in the ash residue during combustion as either sulfate or water-insoluble compounds. The reaction of sodium compounds with the clay minerals in coal resulted in the formation of the insoluble compounds. Addition of sodium chloride to the three low-ash content coals (